Role of the pressure field harmonic oscillations in the flutter and flutter-buffet phenomena of high aspect ratio swept wings

The characteristics of the aeroelastic responses occurring in the transonic regime for high aspect ratio swept wings are analyzed in detail and a comparison between a conventional swept wing and a curved planform wing is presented. Power spectral density diagrams for aerodynamic coefficients are plotted and discussed. The interaction of structural and/or pressure field oscillations are investigated. Structural oscillations refer to the natural vibrations of the wings, while pressure field oscillations concern small variations of pressure in transonic regime that, under specific physical conditions, have the characteristics of a nonlinear multiple-degree-of-freedom resonant system. Transient CFD analyses performed on rigid wings, with modified geometries, provided the frequency contents of the pressure fields allowing investigating their role in critical conditions. The modified geometries were extracted from the results of 2-way fluid structure interaction (FSI) analyses. For a swept-wing model, with straight leading and trailing edges, the aeroelastic deflections strongly influence the transonic buffet onset and a clear interaction between a structural mode and pressure field oscillations occur. Conversely, for a curved planform wing, although the pressure field fluctuates significantly, this work demonstrated that transonic pressure field oscillations do not interact with the wing’s structural modes.